1. Technical Field
The invention concerns extruded plastic profiles with integrated insulation and the method and apparatus for extruding such products.
2. Background Information
Milled wood products have formed the foundation for the fenestration, decking, venetian blinds, shutters, decking and remodeling industries for many years. Historically, ponderosa pine, fir, red wood, cedar and other coniferous varieties of soft woods have been employed with respect to the manufacture of residential window frames, residential door frames, residential siding, outer decking and exterior shutters as well as interior venetian blinds and shutters. Wood products of this type inherently possess the advantageous characteristics of high flexural modulus, good screw retention, easy workability (e.g., milling, cutting), easy paintability, and for many years, low cost. Conversely, wood products of this type have also suffered from poor weatherability in harsh climates, potential insect infestation such as by termites, and high thermal conductivity. In addition, virgin wood resources have become scarce causing correspondingly high material costs.
Alternatively, various metals, especially extruded aluminum, have been used and continue to be used as residential window and door frames in addition to commercial window and door frames. Metal products of this type inherently possess the advantageous characteristics of high flexural modulus and easy paintability, but also suffer from high thermal conductivity.
The high thermal conductivity of both milled wood products and extruded aluminum have become particularly disadvantageous for the window and door products of the fenestration industry. Due to increasing energy costs and increased awareness and concern over energy usage in residential housing, there is governmental regulatory pressure from building codes, product certification requirements, incentive programs subsidizing the purchase of thermally efficient residential housing windows and door products, and general market demand for ever more thermally efficient windows and door products.
In response to the above described disadvantages of milled wood products and metal products, the fenestration industry, in particular, adopted polyvinyl chloride (PVC) as a raw material. Hollow, lineal extrusions manufactured into window frames became an enormous success, particularly at the lower end of the price spectrum. The window frames and sashes made from hollow PVC lineals (often referred to as “vinyl windows”) have exhibited superior thermal conductivity compared to painted ponderosa pine window or extruded aluminum. Further, foamed polymer solid extrusions have been used to replace wood window frames and sashes. The foamed polymer extrusions may contain organic or inorganic fillers, such as wood flour and talc, respectively, where advantageous for improved physical properties such as stiffness and/or to reduce the cost of the extrusions.
Due to the high thermal conductivity of extruded aluminum window and door frames, and even to further improve the thermal performance of vinyl windows and doors formed from hollow PVC lineals, the fenestration industry has inserted foam insulation into the hollow interior portions of the extrusions. This insulation can significantly improve the thermal performance of a window or door frame, and therefore improve the thermal performance of the entire window, by reducing the free air within an interior pocket or chamber of the hollow extrusion. This free air within a chamber of the extrusion can cause significant heat transfer through the walls of the extrusion due to the temperature difference between the inside and outside walls of the extrusion causing the air to cycle around in the cavity causing convective heat loss in the associated window. The insulation within hollow can reduce or eliminate this convection heat transfer. The determination of which pocket or chamber within the window or door frame extrusion would see the most benefit from such insulation is dependent on the particular shape of the window extrusion and window and is determined on a case-by-case basis based on thermal simulations or sample testing.
One commonly used prior art foam insulation is a low density block polystyrene based foam, often referred to as Styrofoam, which is cut or otherwise dimensioned to fit within the desired pocket or chamber within the window or door frame extrusion. Such a polystyrene block will insulate well should it substantially fill the chamber, but achieving this proper fit is the significant disadvantage. Rarely are the pockets or chambers within the window or door frame extrusion a standard or regular size, so that usually the polystyrene will have to be cut down from a block or sheet causing scraps and wasted insulation. Inserting the polystyrene insulation into the pocket or chamber within the window or door frame extrusion can be difficult if the clearance between the exterior of the polystyrene insulation and the chamber are too tight, but too large air gaps between insulation and extrusion will diminish the thermal performance. Thus, this can be a significantly labor intensive and costly process.
A second prior art foam insulation is a low density, CFC free, semi-rigid polyurethane foam. This is typically an in-place foam process that uses equipment to mix two ingredients together where this mixture is then injected and expands within the chamber to be insulated. An example of this prior art foam insulation is FOAMSEAL® P12844/FSA sold by Futura Coatings of St. Louis, Mo. This process is another process step for a window or door manufacturer which adds labor costs. Further, both the polystyrene foam and the polyurethane foam are separate materials from either the extruded aluminum or the PVC lineals that make up the window frames making it more difficult to recycle the base materials.
As above, an advantage of windows manufactured with wooden frames and sashes is that they can easily be stained or painted virtually any color. Thus, the color of the window frame and sash could be chosen to accent or contrast with the color of the exterior of the house. The prior art PVC products are typically available only in white or beige or other colors that do not readily absorb in the IR spectrum and therefore do not build up sufficient heat to distort the body of the extrusion. Typically, these mono-color extrusions are seen in lighter shades and pastels where heat build-up is not a problem and where the required amount of pigments does not unduly increase the cost of the extrusion.
Understandably, window and door profiles in dark colors, such as “Hunter Green” and “Bronze,” have long been demanded in the industry and available in wood or extruded aluminum which has been a significant market advantage of such products. When referring to dark colors herein, the inventor is referring generally to colors with an Lh value between 13 and 40. For example, per ASTM 4726-02, dark brown is defined as a color with an Lh between 13 and 33, an ah between −1.0 and 6.0 and a bh between 1.0 and 6.5. Per AAMA 308-02, dark green is defined as a color with an Lh between 20 and 40, and ah between −20 and −2 and a bh between −2.0 and 4.0. The inventor defines the color red to have Lh values between 20 and 30, ah values between 13 and 23, and bh values between 6 and 12.
Applying a thin capstock layer to hollow vinyl profiles and solid foamed polymer resin extrusions is well known in the art. Typically, the capstock layer is applied for the purpose of achieving color, weatherability, and certain appearance attributes in a cost-effective manner. Frequently, this allows the practitioner to use a lower-cost material in the substrate and therefore reduces total product cost. However, in the past, the useful color spectrum that can be applied to PVC hollow or foamed profile extrusion is limited to colors and pigment systems that do not build up excessive heat and thereby cause the body of the product to distort.
Assignee of this application has been assigned co-pending U.S. patent application Ser. No. 11/291,494 entitled “Low Heat Build-up Capstock System and Extrusion Technology for Solid and Foamed Profiles in Dark Colors” which allows the production of a dark colored capstock that is significantly NIR transparent rather than NIR reflective, and relies on an NIR reflective substrate for the NIR reflectance and allows a dark colored capstock on hollow PVC extrusion. Disclosure of that application is incorporated herein by reference.